Hello! First, I'm French Canadian, so sorry for my mistakes. I have a some issues with Apple Motion. My biggest concern is that I'm not able to use Optical Flow properly anymore. It started after I used Onyx I think. Whenever I send a clip from FCP to Motion, and then change its properties to slow down the clip with Optical Flow, the spinning wheel that indicates Motion is processing the information doesn't appear.
Then, Motion is very buggy now (a legal version). I'm not even able to open the Preferences window, some windows don't open unless I make some twisted manipulations, etc. What worked like a charm some months ago is a real mess now.
I even uninstall the whole package (FCS) and reinstall it and I have the same problems again (and the shortcuts in FCP don't work either).
First try to delete the preferences of motion which is in the library/preferences. Then try to open motion and go to preferences I think edit menu then at the bottom select preferences. Then look to find optical flow cach and purge or delete the cash of optical flow. Let me know did it work.